Multilayer, coextruded, ionomeric decorative surfacing

ABSTRACT

Decorative ionomeric surfaced film and sheet (e.g., multilayer co-extruded polymer) and articles made therefrom (e.g., automotive panels and parts) exhibiting good weatherability, mar resistance, and surface appearance of a high quality automotive finish (including color, haze, gloss, and DOI) and economical process for making (e.g., co-extrusion) and using (e.g., thermoforming and injection backfilling) the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 11/827,257, filedJul. 11, 2007; which is a division of application Ser. No. 09/833,452,filed Apr. 12, 2001, allowed; which claims the benefit of priority toprovisional application 60/197,275 filed Apr. 14, 2000; the entiredisclosures of the parent applications are herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to multilayer, co-extruded, ionomericthermoplastic sheet and film, articles manufactured with a decorativesurface of such sheet and film, and processes for making shaped articleshaving a top surface of decorative ionomeric film.

2. Description of the Related Art

To describe the background of the present invention in this section andvarious components used in the invention, various patents arereferenced. Each of these patents is incorporated herein by reference.

There is an increasing need, particularly in the automotive industry,for panels and parts made of polymer materials. Use of such polymerpanels and parts provide numerous benefits. For example, weight of thefinished assembly is reduced (important for automobiles), capital costsassociated with plastic are lower than with metal, styling freedom isincreased (important in automotive industry where there are more andmore model demands), and manufacturing (plastic tooling) costs arelowered.

Use of such parts and panels, however, has been limited by variousproblems. Typically, polymer surfaced panels do not present a surfaceappearance comparable to a high quality automobile finish or do notprovide a good bonding surface for the paints needed to achieve the highquality finish. Furthermore, high quality painting can be costly andpresent significant environmental, as well as safety and healthproblems, particularly those associated with volatile organic carriersused in paints. Other concerns with polymer parts include suitableproperties and durability of those properties with extended outdoorexposure, including high gloss appearance, impact strength, hightemperature properties (e.g. tensile strength and dimensionalstability), low temperature properties, durability, scratch and marresistance, and distortion of appearance at weld lines and with complexparts such as those made with deep draw. Attempts to solve theseproblems have met with mixed success.

Producing a surfacing film with paint like appearance has experiencedlimited success due to problems in processing films onto articles andunattractive economics for films in replacing paint. Fashioning asurfacing (skin) film system that can replace paint appearance ischallenging since the film is required to meet many specificationsincluding appearance that is similar to paint in both solid and metalliccolors. In metallic paint application, a special effort must be made tocontrol the size of the effect particles and the particles' orientationin painted surfaces in order to exhibit the desired metallic appearance.Flat or higher aspect ratio (length to thickness) effect particles inpaint formulations are applied in ways to obtain a flat or parallelorientation with the surface. A variable characterizing this particleorientation in paint is called flop, and is calculated from colormeasurements (L values) obtained at different angles from the lightsource. Duplicating this metallic appearance inexpensively with apolymer surface skin system that has the other necessary surfaceattributes of high gloss, durability in outdoor exposure, chemicalresistance, impact resistance, layer adhesion, temperature resistanceand other properties has met very limited success based on a very smalldecorated surface market share for plastic colored skins.

Decorative composite surfacing films made from a liquid solvent ordispersion system such as those disclosed in U.S. Pat. Nos. 4,810,540;4,931,324; 4,943,680; and 5,342,666 have been used. Dry paint transferproducts such as those taught in U.S. Pat. No. 5,707,697 have been used.U.S. Pat. No. 5,985,079 teaches melt extrusion coating as a zero-solventapproach to clear coat production and co-extrusion as an approach tobase coat/clear coat production for certain colors. EP 0 949 120 A1presents a flexible, weatherable decorative sheet material that has anextruded base layer with a clear outer layer of extruded film as anoverlay. A color adjustment layer of printing ink can be includedbetween the base layer and the clear coat.

Reissue of U.S. Pat. No. 5,514,427 (Re. 36,457) purports to solve theproblems presented by the PVC and films such as the Tedlar® filmsmarketed by E. I. du Pont de Nemours and Company through the use of asubstantially molecularly unoriented cast polymer film prepared byliquid casting methods. Typically these liquid cast films requiremultiple step processes to provide sheet attributes suitable forthermoforming and adhesion properties for injection cladding, as surfaceskins that provide a paint-like appearance. Often in these films, thepolymer, pigment and effect particles are cast onto a high gloss filmfrom a solution followed by solvent evaporation. In other filmconstructions, the pigment and effect particles may be printed onto thesurface in order to provide the desired metallic effect orientation andappearance such as provided by a paint. Often though these films are notcommercialized due to uneconomical cost in materials or processing ordeficient attributes such as appearance degradation after thermoformingdue to the thin pigment carrying layer or the thin pigment layerstreaking after elongation.

Another approach has been to make a “solid” part with molded-in color.Bexloy®W automotive engineering resin, a blend of ionomer andpolyethylene sometimes reinforced by glass fiber, marketed by E. I. duPont de Nemours and Company, for instance, has found increasing use inmolded parts such as automobile bumpers. Solid color can be incorporatedinto the material, but success in incorporating metallic colors has beenlimited. Also, paint adherence to Bexloy®W resin is poor and paintapplication that requires use of high temperature paint baking ovens(Original Equipment Manufacturing “OEM” Painting) is not feasible sinceBexloy®W lacks suitable high temperature properties. To enhance marresistance, a light grain is typically applied to this materialresulting in a loss of “Distinctness of Image” (DOI), a key index usedto evaluate the perceived quality of an exterior finish in theautomotive industry.

Another “solid” material that has been used is Surlyn® ReflectionsSeries™ resins, an ionomer-polyamide blend, marketed by E. I. du Pont deNemours and Company. Molded parts made from this engineering materialretain important performance characteristics of the Bexloy® W, have highgloss exhibiting DOI's at least comparable to the best of paint finisheson smooth or “Class A” surfaces, particularly DOI's over 80 and as highas 90 to 95. Solid and metallic colors can be incorporated and parts canbe painted. High temperature properties are sufficient to permit OEMPainting without the need for special jigs or hangers to maintain partshape during the bake step. See U.S. Pat. No. 5,866,658.

By molding in color, certain capital, operating, and pollution abatementcosts, particularly those associated with paint and solvent systems, canbe eliminated. The solid parts have more durability and exhibit fewerdefects as a result of weathering, chemical attack, and chipping thanpainted parts in use. However, they can exhibit splay, ghosting, flowlines and, in the case of a flake or particle with an aspect ratio,“metallic flow lines” which are often objectionable flow induced visualimperfections that particles in the polymer highlight due to lightreflection and scatter. Solid injection molded parts can be uneconomicalsince the higher value polymer that provides the desired surfaceattributes is typically much thicker than needed to provide just theattributes of the surface, and in many cases the entire thickness of thepart may be the higher value polymer.

Japanese patent application (Kokai) No. SHO 58(1983)-155953, teaches theconcept of making a laminated molding body with a polyolefin layer and asurface layer made from a metal salt of an ethylene-α,β-unsaturatedcarboxylic acid copolymer having a glossy surface after lamination.Although the reference teach generally that there are no speciallimitation on the method used for laminating the base layer (polyolefin)to the surface layer (ionomer) with or without an intermediate adhesivelayer which included co-extrusion, the working examples deal exclusivelywith hot pressing a commercial grade ionomer film (Surlyn® A1652) to a 2mm thick polyolefin sheet of polypropylene or ethylene-propylene blockcopolymer. Also, the fabrication of the case-shaped product involvedpreheating the laminated sheet and vacuum molding on the side oppositethe die. No mention of multilayer, co-extruded, ionomer film or sheetand any advantage of the same is present in this prior art reference.

BRIEF SUMMARY OF THE INVENTION

The present invention generally relates to a multilayer ionomericthermoplastic sheet (skin) for surfacing polymer parts (or othersubstrates including metal) to provide a high quality surfaceappearance, such as one suitable for interior or exterior automotiveparts, appliance panels, general aviation applications and the like. Thesheet exhibits a colored appearance similar to a surface which ispainted with a solid color or a color containing particles that providea “special effect” to the appearance often referred to as a metallicpaint appearance. The novel methods of fabricating a part according tothe instant invention using the decorative sheet involve both extrudedmonolayer and multilayer sheeting, particularly co-extruded, sheetshaving an ionomeric or ionomer-polyamide blend top surface layerco-extruded onto a selected second polymer layer. Shaped articles madeby thermoforming multilayer co-extruded ionomeric sheets (particularlythose having sufficient thickness to be self-supporting), and articlesformed by back-filling the decorative thermoplastic monolayer sheet orco-extruded sheet according to the methods of the instant invention havea high quality surface appearance comparable to a high qualityautomotive paint finish. The present invention also provides methods forforming shaped polymer articles with the decorative skin sheet on theouter surface thereof.

Among other features, the present invention allows reduced manufacturingcost, reduced material costs, and appearance enhancement throughcontrolled particle orientation and combination of material clarity andtranslucent pigment use with effect particles. In one embodiment,manufacturing of shaped articles can be accomplished in fewer steps thanconventional “dry paint film” by feeding the extruded thermoplasticsheet of the present invention, preferably preheated, directly into aninjection cladding mold for back-filling from a roll of flat sheet thathasn't been preformed. Sheeting of this invention reduces surfaceimperfections such as ghosting, flow lines, and glass marks, andmetallic appearance problems associated with injection molded parts. Itovercomes the processing drawbacks of some fluoropolymer containing skinfilms in deeper draw thermoforming such as streaking. The presentinvention allows great flexibility and improved economy in making partswith Class A surface by using backfill materials with the thermoformablesurface sheet. Finished part properties and costs can be tailored byvarying the backfill material, by adding stiffening or other componentsto the backfill material, by special processing of the back-fillingmaterial (e.g., foaming) or by trim or off quality material inclusion inthe backfill material.

The decorative sheet of the present invention is a multilayer sheetwherein the top layer of the multilayer sheet comprises an ionomer orionomer-polyamide blend. The thermoformable sheet can be made in a sheetmultilayer melt extrusion process with pigment and flake particles inthe surface layer or other layers of the sheet extrusion process. In thecase of an ionomer surfaced sheet construction, a patterned or designedfilm or sheet can be extrusion coated with or laminated to the ionomersheet with the design or pattern showing through.

The process for making sheet with the ionomer or ionomer-polyamide blendsurface layer overcomes deficiencies and economic constraints ofexisting polymer based “paint films”. Multilayer sheet co-extrusionprocessing provides pigment carrying layers of sufficient thickness thatthey maintain appearance and hiding power following deep drawthermoforming, control of machine direction effect particle orientationto allow satisfactory replication of paint appearance and one stepprocessing (excluding subsequent thermoforming, cladding, and/ortrimming steps etc.) which improves the economics for competition withpaint systems.

The shaped plastic article of the present invention has a high qualitysurface appearance comparable to a high quality automotive paint finish.It can be a thermoformed sheet or a back-filled thermoplastic sheet.

Thus the present invention provides multilayer film or sheet comprising:

-   -   a.) a first co-extruded polymeric layer consisting essentially        of ionomer; and    -   b.) at least one co-extruded second polymeric layer selected        from the group consisting of ionomer, ionomer-polyethylene        blend, and ionomer-polyamide blend in contact with the first        co-extruded polymeric layer.

The present invention further provides a multi layer film or sheetcomprising either:

-   -   a.) a first co-extruded polymeric layer consisting essentially        of ionomer; and    -   b.) at least one co-extruded second polymeric layer consisting        essentially of very low density polyethylene in contact with the        first co-extruded polymeric layer; or    -   a.) a first co-extruded polymeric layer consisting essentially        of ionomer; and    -   b.) at least one co-extruded second polymeric sheet layer        consisting essentially of ethylene polar copolymer in contact        with the first co-extruded polymeric layer; or    -   a.) a first co-extrusion polymeric layer consisting essentially        of ionomer-polyamide blend; and    -   b.) at least one additional co-extruded second polymeric layer        in contact with the first co-extrude polymeric layer.

In each of the above embodiments the multilayer film or sheet mayfurther comprise at least one additional co-extruded third polymericlayer in contact with the second co-extruded polymeric layer. Theethylene polar copolymer co-extruded second layer is preferably an acidfunctionalized copolymer when the top surface is an ionomer layer. Thesecond polymeric layer is preferably a maleic anhydride functionalizedpolymer when the top surface layer is an ionomer-polyamide blendco-extruded. Preferably one or more of the co-extruded polymeric layerscontain pigments, dyes, flakes, or mixtures thereof. The thirdco-extruded layer can be a very low density polyethylene.

The ionomer preferably consists essentially of a copolymer derived fromethylene and α,β-ethenically unsaturated C₃ to C₈ carboxylic acidwherein the copolymer is partially neutralized with metal ions. Theionomer-polyamide blend consists essentially of one or more polyamidewhich forms a continuous phase or co-continuous phase with one or moreionomer dispersed therein, the ionomer is present in the range from 60to 40 weight percent and the polyamide is present in the range from 40to 60 weight percent based on the total weight of ionomer and polyamide,the ionomer consisting essentially of a copolymer derived from ethyleneand α,β-ethenically unsaturated C₃ to C₈ carboxylic acid wherein thecopolymer is partially neutralized with metal ions; wherein the averageacid content of copolymer prior to neutralization is present in asufficiently high percentage such that neutralization in the range of 55to 100 mole percent of the acid present at melt temperature with one ormore metal cations increases the viscosity of the ionomer above that ofthe polyamide.

The present invention further provides a process for making shapedarticle having an ionomer or ionomer-polyamide blend as a top surfacecomprising the steps of:

-   -   a.) positioning a monolayer sheet of ionomer or        ionomer-polyamide blend or a multilayer co-extruded sheet into a        mold, wherein the thickness of the monolayer sheet or the        multilayer sheet is from 8 to 60 mils and wherein the multilayer        sheet comprises;        -   i.) a first co-extruded polymeric layer selected from the            group consisting of ionomer and ionomer-polyamide blend; and        -   ii.) at least one additional co-extruded second polymeric            layer in contact with the first co-extruded polymeric layer;            and    -   b.) injection backfilling the monolayer sheet or multilayer        co-extruded sheet with a suitable backfilling material.

Preferably the sheet is preheated prior to the injection backfillingparticularly for thick sheet and sheet of higher melting pointionomer-polyamide blends. In one embodiment of this process themultilayer sheet comprises;

-   -   (i) a first co-extruded polymeric layer consisting essentially        of ionomer;    -   (ii) a second co-extruded polymeric layer selected from the        group consisting of ionomer and ionomer-polyamide blend in        contact with the first co-extrude polymeric layer; and    -   (iii) at least one additional co-extruded third polymeric layer        in contact with the second co-extrude polymeric layer.

The present invention further provides a process for making athermoformed, multilayer, sheet-surfaced article comprising the stepsof:

-   -   a.) positioning a multilayer sheet into a mold, wherein the        thickness of the multilayer sheet is from 8 to 60 mils and        wherein the multilayer sheet comprises;        -   i.) a first co-extruded polymeric layer selected from the            group consisting of ionomer and ionomer-polyamide blend; and        -   ii.) at least one additional co-extruded second polymeric            layer in contact with the first co-extrude polymeric layer;            and    -   b.) raising the temperature of the sheet sufficiently to soften        the multilayer sheet; and    -   c.) conforming the softened sheet to the contoured surface of a        substrate in the mold.

In one embodiment of this process the multilayer sheet comprises;

-   -   (iv) a first co-extruded polymeric layer consisting essentially        of ionomer;    -   (v) a second co-extruded polymeric layer selected from the group        consisting of ionomer and ionomer-polyamide blend in contact        with the first co-extruded polymeric layer; and    -   (vi) at least one additional co-extruded third polymeric layer        in contact with the second co-extrude polymeric layer.

Thus the present invention provides an article consisting essentially ofa substrate to which a multilayer film or sheet is adhered, wherein themultilayer film or sheet comprises either:

-   -   a.) a first co-extruded polymeric layer consisting essentially        of ionomer; and    -   b.) at least one co-extruded second polymeric layer selected        from the group consisting of ionomer, ionomer-polyethylene        blend, and ionomer-polyamide blend in contact with the first        co-extruded polymeric layer; or    -   a.) a first co-extruded polymeric layer consisting essentially        of ionomer; and    -   b.) at least one co-extruded second polymeric consisting        essentially of very low density polyethylene in contact with the        first co-extruded polymeric layer; or    -   a.) a first co-extruded polymeric layer consisting essentially        of ionomer; and    -   b.) at least one co-extruded second polymeric sheet layer        consisting essentially of ethylene polar copolymer in contact        with the first co-extruded polymeric layer; or    -   a.) a first co-extrusion polymeric layer consisting essentially        of ionomer-polyamide blend; and    -   b.) at least one additional co-extruded second polymeric layer        in contact with the first co-extrude polymeric layer.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of this invention the following terms are to be defined asfollows:

-   -   1. “Copolymer” means polymers containing two or more monomers        and as such the term is intended to include both “bipolymer” and        “terpolymer” as well as polymers produced from more than three        comonomers. The terms “bipolymer” and “terpolymer” mean polymers        containing only two and three monomers respectively. The phrase        “copolymer of various monomers” means a copolymer whose units        are derived from the various monomers.    -   2. “(Meth)acrylic acid” means acrylic acid and methacrylic acid,        and the term “(meth)acrylate” means acrylate and methacrylate.    -   3. “Consisting essentially of” means that the recited components        are essential, while smaller amounts of other components may be        present to the extent that they do not detract from the        operability of the present invention.    -   4. “Distinctness of Image” (DOI) is a measure of the “crispness”        or “degree of definition” of a reflection of a object in a        colored finish compared to the actual object itself. (DOI) is        defined in ASTM Standard-284 as: distinctness-of-image-gloss,        n-aspect of gloss characterized by the sharpness of images of        objects produced by reflection at a surface. DOI can be measured        with a BYK-Gardner Wavescan doi instrument bases on U.S. Pat.        No. 1,155,558. In the automotive industry, satisfactory finishes        on a smooth or “Class A” surface typically will have a finish        with a DOI value of at least 60, preferably 80 or higher.    -   5. Flop is an expression and a calculated variable used to        describe or characterize appearance change with viewing angle.        In its calculated term context, it is calculated from color        measurement L values at 3 different angles from a light source.        The higher the flop value, the greater the appearance change in        viewing at different angles.    -   6. Effect particle is a particle added to paints or pigments        which provides an appearance effect or change in color with view        angle. Typical effect particles are aluminum flakes and mica        particles. Often effect particles are flat and thin and their        orientation can be important in imparting a certain appearance.    -   7. Machine direction (MD) means the orientation in a film which        is in the direction, either upstream or downstream, that the        film is exiting the machine or die. The MD direction can be        referred to as either pointing into the machine or away from the        machine, 180 degrees apart. The term can be associated with film        length. This is in contrast to the cross machine direction or        “TD” direction which is the direction 90 degrees from the        machine direction or exit flow direction and typically indicates        the direction across the film width from one side to the other        side.    -   8. CIELAB color difference is defined in ASTM Standard-284 as,        n-color difference calculated by using the CIE 1976        L*a*b*opponent color scales, based on applying a cube-root        transformation to CIE tristimulus values X,Y,Z.    -   9. Gloss is defined in ASTM Standard-284 as, n-angular        selectivity of reflectance, involving surface reflected light,        responsible for the degree to which reflected highlights or        images of objects may be superimposed on a surface.    -   10. Haze is defined in ASTM Standard 284 as: n-scattering of        light at the glossy surface of a specimen responsible for the        apparent reduction in contrast of objects viewed by reflection        from the surface.    -   11. A Class A surface is a surface that by itself of when        painted results in DOI, gloss and haze readings of 80, 90, 10.

It should be further appreciated that for purposed of the presentinvention, the use of the expressions multilayer film and the multilayersheet refer collectively to polymeric films and sheets that are fromabout 1 mil to about 60 mils thick. Although no single thicknessdimension is felt to represent a demarcation between film and sheet, forpurposes of this invention the use of the word sheet, in both theprocesses for making a shaped article involving backfilling of sheet andfor making a thermoformed article from sheet, refers to polymericmaterial of 8 to 60 mils thick.

Film Process

Lamination and melt extrusion processes known in the art can make thethermoformable sheet of the present invention. Multilayer sheets can bemade on extrusion lines that may be configured and operated in waysknown in the art. The monolayer or multilayer sheets of the presentinvention may be laminated or coated as the surface layer onto othersubstrate sheets to form decorative sheet structures.

In a typical extrusion system, selected solid plastic particles inpellet form are fed to an extruder, melted and plasticated, pumpedthrough a transfer pipe into a feedblock and then to an extrusion die ordirectly to a die. The molten curtain that exits the die is depositedonto a moving roller which transfers the solidifying polymer through agap or nip between two counter-rotating rollers to a third roller andsubsequently through another nip system between rollers which pulls thesheet through the take-off system. The sheet is subsequently rolled ontoa core creating a roll of sheet or the sheet can be cut to a length andstacked as flat sheets.

In a typical system for making multilayer sheet, there are multipleextruders into which particles are fed, melted and plasticated by theextruder screw and heated barrel system. The resulting molten mass canbe pumped through a transfer pipe into a co-extrusion feedblock for thepurpose of combining the flows into contacting layers. The feedblock canbe equipped with a plug that can be changed to allow differentcombinations of extruders and layers to be run on the line. The plugroutes the flows within the feedblock and combines the layers prior toexiting the feedblock and going into an extrusion die. The extrusion diehas a flow area or manifold that widens and thins the single ormultilayer melt flow into a thinner, wider web or melt curtain. Themultilayer molten flow is widened and thinned to the die flow width anddie gap opening.

The “match” in rheology between the layers will determine how well thelayers spread together in the die. If there is a significant differencein flow properties, the layers may not all flow to the width of the die.In this case, lower viscosity material may flow to the end of the dieopening and higher viscosity material flow width will be less. If thelayer flow properties are well matched, each layer will flow to the fullwidth of the die. Finally, if the flow properties are poorly matched,quality sheeting may not be produced due to flow instabilities betweenlayers in the die and air gap exit the die.

Alternatively, a different type of extrusion die, a multiple manifolddie, can be used in place of the “extrusion feed block and singlemanifold die” arrangement. In this case, separate extruder melt streamsflow directly into separate flow paths or manifolds within a multiplemanifold die. Each layer in this case flows through its own manifold andis spread and thinned to the width of the die flow area prior to thelayers combining and flowing together into a multilayer molten sheet.The combination of layers in this case, occurs near the die exit aftereach layer has been thinned and widened separately and is therefore lesssensitive to mismatch in flow properties. In a similar fashion, morethan 1 layer can be fed into a separate manifold where the multiplelayers can be spread and thinned in the manifold.

The molten flow exits the die as a molten curtain and flows onto a metalroller just prior to contacting a large diameter roll. These rolls arecounter rotating. The gap between these rollers is set to provide auniform opening, referred to as a nip. The molten plastic contacts bothrolls as it is conveyed through the controlled opening gap. The rollarrangement provides a higher glossy finish on the sheet and moreuniform thickness to the sheet. The primary roller is a highly polishedroll that is contacted by the sheet for approximately half of itscircumference prior to releasing the solidifying plastic typically to athird roll downstream in the takeoff roller system. The sheet issubsequently taken through another nip system between rollers whichpulls the sheet in the system. The sheet is subsequently rolled onto acore creating a roll of sheet or alternatively can be cut to length andstacked.

In practice, there are several alternatives for the molten flow exitingthe die. For example, the die can be repositioned to drop the moltencurtain so as to contact the larger roll initially just prior to thenip. Another example arrangement positions the die at angles betweenvertical and horizontal to result in vertical or horizontal molten flowfrom the die. Also, instead of a second roll providing a nip, othermeans can be used to force the molten plastic onto a roll such as airflow pushing the molten web onto a roller.

Co-extrusion Sheet:

The appearance of sheet from the sheet process can have severalvariables that effect its appearance and performance. The sheet can havea clear surface layer with under layers containing pigments and effectparticles in the case of the ionomer sheet or it can have a pigmentedsurface layer with or without effect particles as is the case with theionomer-polyamide blend. One or more of the under layers in either casemay contain pigment or particles.

The sheet appearance can be changed with the blend of pigments used andwith the orientation of the effect particles if they are present.Ideally for solid color pigmentation only, the color would not changebased on viewing direction for a flat sheet if the purpose is to match atypical paint appearance surface. However, effect particles in sheetextrusion encounter multi axial particle orientation that effects colorand appearance. It has been found that orientation of the flakeparticles toward a particle that is closer to parallel with the surfacecan be controlled in sheet extrusion to a certain extent with the properequipment and operating techniques. This is necessary to provide acloser match to painted surfaces, to minimize color difference based onviewing direction and to minimize color differences between a pigmentedsheet product and a painted surface.

It has been found that flop value differences calculated from colormeasurements in the upstream and downstream MD directions of a sheetproduct could be minimized which in turn minimizes color differencesbased on viewing direction. A single manifold die with the gap opened toa significant degree provided flop difference values of less than about2 whereas when the die is run with a die gap opening considered moretypical, flop values were approximately 4. The die does not have a shortland length. On another die with 2 manifolds and a short die landlength, flop differences were found to be higher than 3 at typical, lowand high gap settings and not effected by gap. Based on this preliminarylimited data particle orientation characterized by flop calculations,can be effected by a combination of both die gap and die exitcharacteristics.

Metallic appearance can be effected through a combination of layerinherent clarity, translucent pigments and effect particles used in alayer which in combination allows flat metallic surfaces to be seen withless light scattering and to a greater depth enhancing appearance andaccentuating the flop or change in appearance with viewing angle that isa desirable attribute. To provide hiding power so undesirable lightreflection from underlying surfaces or layers are minimized, a thicklayer carrying the pigment and flake can be employed, or a higherconcentration of pigment and flake can be used or an under layer withpigment and/or flake can be utilized to effect appearance.

The combination of clear/color layers of either ionomer-ionomer orionomer-acid copolymer as the first two layers in the sheet provide thedesirable characteristics of the surface layer with mar resistance, highclarity, durable in outdoor exposure, chemical resistance and high glossin combination with a second clear layer that has good compatibility foradhesion, minimum distortions from interface disturbances that can becaused be flow differences and appearance attributes described above. Inaddition, ionomer over other layer materials such as EVA's orE-acrylates or PE type materials may also provide a satisfactoryappearance system although these systems may not provide the high levelsof adhesion or the depth and distinctiveness of metallic particlereflection.

Additives that go into the appearance layers may require compatiblecarriers to minimize resultant haze that can be generated by materialincompatibility causing light refraction at the incompatible interface.Additives include pigment or effect particle carriers, UV additivecarriers or anti-static additive carriers. Compatible carrier materialsinclude ionomer, acid copolymer, EVA, E-acrylate copolymers orderivatives.

Thermoformable Skin

The thermoformable skin of the present invention has attributes that caninclude good formability and release from tooling in thermoforming,excellent DOI, high gloss and low haze surface appearance, solid andmetallic color appearance, good mar and scratch resistance, goodweatherability, good impact resistance and good chemical resistance. Itmay be formed into a weatherable, decorative sheet for surfacing polymerparts. The sheet is surfaced with an ionomer or ionomer-polyamide blend.

The ionomers and the ionomer-polyamide blends useful in the presentinvention are described below. The decorative sheet can be monolayer ormultilayer. When a multilayer, at least the top layer of the multilayersheet is made from the ionomer or ionomer-polyamide blend.

The monolayer sheets preferably are about 1 to about 50, alternativelyabout 2 to about 20, mils thick. The multilayer sheets preferably areabout 8 to about 60, alternatively about 12 to about 40 mils thick.However it should be appreciated that thicker dimension such as 60 to400 mils, alternatively 80 to 180, can be easily achieved and retainmany of the benefits of the instant invention for thermoforming largerparts requiring greater stiffness.

Multilayer skin films can be tailored to fit the needs of a wide varietyof specific applications. For example, layers in the skin structure canprovide pigmented solid color, pearlescent pigment and/or other nacreouspigment for colored metallic appearance properties (see U.S. Pat. No.6,060,135 and in particular column 4, lines 25-40, incorporated hereinby reference), stiffness for handling, thermoforming properties, layeradhesion function and a back side layer which will adhere to a backfillmaterial to form a shaped molded article.

Some typical skin constructions include (where slash mark representslayer interface and parentheses designate additive):

Ionomer monolayer (clear or pigmented)

Ionomer-polyamide blend monolayer (pigmented)

Ionomer (clear)/polyethylene-ionomer blend (pigmented)

Ionomer (clear)/polyethylene-elastomer blend (pigmented)

Ionomer (clear)/ionomer (pigmented)/ethylene copolymer

Ionomer (clear)/ionomer (pigmented)/very low density polyethylene

Ionomer (clear)/ethylene acid copolymer (pigmented)/very low densitypolyethylene (pigmented)

Ionomer (clear)/ethylene acid copolymer (pigmented)/very low densitypolyethylene/olefinic thermoplastic

Ionomer (pigmented)/ionomer (pigmented)/ethylene acid copolymer

Ionomer (pigmented)/ethylene acid copolymer

Ionomer (pigmented)/terpolymer ethylene-acid-acrylate(pigmented)/olefinic thermoplastic

Ionomer (pigmented)/terpolymer ethylene-acrylate-glycidal methacrylate(pigmented)/olefinic thermoplastic

Ionomer (clear)/terpolymer ethylene-acid-acrylate (pigmented)/olefinicthermoplastic

Ionomer (clear)/terpolymer ethylene-acrylate-glycidal methacrylate(pigmented)/olefinic thermoplastic

Ionomer (clear)/ionomer (pigmented)/terpolymerethylene-acrylate-glycidal methacrylate/olefinic thermoplastic

Ionomer (clear)/ethylene-acrylate copolymer (pigmented)/ethylenecopolymer

Ionomer (clear)/ionomer (pigmented)/ethylene copolymer/polyethylene

Ionomer (clear)/ionomer (pigmented)/ethylene copolymer/polyestercopolymer

Ionomer (clear)/ionomer (pigmented)/polyamide (pigmented)

Ionomer (clear)/ionomer (pigmented)/tie layer (pigmented)/thermoplasticpolyolefin

Ionomer (clear)/ionomer (pigmented)/tie layer/thermoplastic polyolefin(pigmented)

Ionomer (clear)/ionomer (pigmented)/polyethylene-ionomer blend

Ionomer (clear)/ionomer (pigmented)/tie/nitrile copolymer

Ionomer-polyamide blend/tie/thermoplastic polyolefin

Ionomer-polyamide blend/tie/polyester copolymer

Ionomer-polyamide blend/tie/nitrile copolymer

Ionomer-polyamide blend/polyamide copolymer

Ionomer (clear)/ionomer (pigmented)/tie layer/thermoplastic polyolefin,

Ionomer/ionomer (pigmented)/tie layer/polyester copolymer,

Ionomer/ionomer (pigmented)/tie layer/recycle/tie layer/polyestercopolymer,

Ionomer/polyamide (pigmented)/tie layer/polyester, and

Ionomer/polyamide (pigmented)/tie layer/recycle/polyester copolymer.

The decorative sheet may be adhered to a wide variety of substrates toprovide a high quality surface appearance, such as one suitable forinterior or exterior automotive parts or other panels. It may be used asdecorative “thin” surface layer on “thick part” plastic substrates thatcan be subsequently thermoformed into an article.

Pigmented ionomer-polyamide blend and clear ionomer over a pigmentedsubstrate can provide valuable surface attributes for plastic parts,especially those that are now painted.

Optionally, pigment and/or flake particles may be included in thesurface layer or other layers in the case of a multilayer sheet process.In the case of an ionomer sheet construction, the ionomer can be coatedor laminated onto a patterned or designed film or sheet with the designor pattern showing through.

The high temperature properties of the ionomer-polyamide blend aresufficient to permit OEM Painting of molded parts without the need forspecial jigs or hangers to maintain part shape during the bake step.

Shaped Article Forming Process

Shaped articles employing the decorative thermoplastic sheet of thepresent invention can be made by processes known in the art includinginjection cladding, compression molding and direct thermoforming. Thedecorative thermoplastic sheet can also be laminated onto a substrate toform an article.

A particularly useful method is injection cladding such as described inU.S. Pat. No. 5,725,712 (incorporated herein by reference, see columns16 through 20). The decorative thermoplastic sheet or co-extruded sheetcan be back-filled with a wide variety of backfill materials. The flatsheet, preferably preheated, can be moved directly into an injectioncladding mold for back-filling without thermoforming the sheet first. Bypreheating, deep-draw shapes can be made without creasing problems.

Direct thermoforming is particularly useful when the sheet beingthermoformed by itself is sufficiently thick to provide stiffness andrigidity needed by the article. Particularly useful for making suchdirectly thermoformed articles are co-extruded sheets with surfacematerials of ionomer or ionomer-polyamide blend.

A relatively thin (typically, 15-50 mils) decorative sheet can bethermoformed into a mold's shape and inserted into an injection mold orsheet molding compound (SMC) compression mold for cladding in a two stepprocess.

When using the decorative sheet made from ionomer, it has been foundthat it is not necessary to maintain the gloss of the sheet from startto finish, as it is in “paint film” systems. Instead, the surface glossof ionomers with a low temperature softening point can be improved infinal back-filling step as the film contacts the polished surface of theinjection molding tool in the back-filling step. This property overcomesskin handling mars, reduces skin sheet handling costs and provides for amore flexible and robust process. Preferably, the temperature of theinjection molding tool should be from about 10 to about 50° C. Thetemperature of the back-filling molten polymer should be sufficientlyhigh to soften the ionomer or ionomer-polyamide skin so that it conformswell to the mold and picks up a high gloss.

Shaped Plastic Article

The thermoformable skin discussed above can be formed into a shapedpolymer article with the decorative skin on the outer surface thereof.Shaped articles of this invention include automobile body panels,mirrors, accent pieces, grills, hoods, sport utility vehicle bodypanels, appliance panels and the like. The shaped polymer articles ofthis invention particularly are ones presenting a high quality surfaceappearance comparable to a high quality automotive paint finish. Theyexhibit high gloss, low gloss, or textured appearance and improved marresistance. These molded articles typically exhibit DOI's of at least 80and frequently as high as 90 to 95. Solid and metallic colors can beincorporated and parts can be painted.

Shaped articles employing the thermoformable sheet of this invention asa top layer, particularly with the addition of standard UV stabilizersfor the ionomer and ionomer-polyamide blend, exhibit goodweatherability, being particularly stable when exposed to ultravioletlight for extended periods of time. These articles exhibit the low colorshift, measured using, for example, the CIE 1976 (CIE LAB) color scale,needed for molded parts used in exterior applications. They exhibit ΔEcolor shift values of less than about 3 (a level considered as suitablefor exterior automotive applications) when exposed to 2500kilojoules/square meter in a Xenon-arc weatherometer (SAE J1960).Improved automobile fascia having DOI of at least 80 and superior marresistance can be made employing the thermoformable sheet of thisinvention.

Ionomer

The ionomers of the present invention are derived from direct copolymersof ethylene and α,β ethenically unsaturated C₃-C₈ carboxylic acid(“ethylene-acid copolymers”) by neutralization with metal ions. By“direct copolymer”, it is meant that the copolymer is made bypolymerization of monomers together at the same time, as distinct from a“graft copolymer” where a monomer is attached or polymerized onto anexisting polymer chain. Methods of preparing such ionomers are wellknown and are described in U.S. Pat. No. 3,264,272 (incorporated hereinby reference). Preparation of the direct ethylene-acid copolymers onwhich the ionomers are based is described in U.S. Pat. No. 4,351,931(incorporated herein by reference). Ethylene-acid copolymers with highlevels of acid are difficult to prepare in a continuous polymerizerbecause of monomer-polymer phase separation. This difficulty can beavoided however by use of “cosolvent technology” as described in U.S.Pat. No. 5,028,674 (incorporated herein by reference) or by employingsomewhat higher pressures than those at which copolymers with lower acidcan be prepared.

The ethylene-acid copolymers used to make the ionomeric copolymer ofthis invention can be E/X/Y copolymers where E is ethylene; X is asoftening comonomer and Y is the α,β-ethenically unsaturated C₃-C₈carboxylic acid, particularly acrylic or methacrylic acid. Preferably,however, the ethylene-acid copolymer is a dipolymer (no softeningcomonomer). The preferred acid moieties are methacrylic acid and acrylicacid.

By “softening”, it is meant that the polymer is made less crystalline.Suitable “softening” comonomers (X) are monomers selected from alkylacrylate, and alkyl methacrylate, wherein the alkyl groups have from1-12 carbon atoms which, when present, may be up to 30 (preferably up to25, most preferably up to 12) wt. % of the ethylene-acid copolymer.

Preferred ethylene-acid dipolymers are ethylene-acrylic acid andethylene-methacrylic acid. Specific other copolymers includeethylene-n-butyl acrylate-acrylic acid, ethylene-n-butylacrylate-methacrylic acid, ethylene-iso-butyl acrylate-methacrylic acid,ethylene-iso-butyl acrylate-acrylic acid, ethylene-n-butylmethacrylate-methacrylic acid, ethylene-methyl methacrylate-acrylicacid, ethylene-methyl acrylate-acrylic acid, ethylene-methylacrylate-methacrylic acid, ethylene-methyl methacrylate-methacrylicacid, and ethylene-n-butyl methacrylate-acrylic acid (where the dashrepresents comonomers).

The mole percent acid moiety (i.e., mole percent of carboxyl group,—COOH, relative to an elemental mole basis) in the ethylene-acidcopolymer prior to neutralization in the ionomer employed by itself as alayer preferably is 0.54 to 1.26%, alternately 0.68 to 1.11%, or 0.82 to0.96% and the degree of neutralization preferably is 30 to 100%,alternately 40 to 80%, or 45 to 70%. On a polymer mole basis, the molepercent acid moiety in the ethylene-acid copolymer prior toneutralization in the ionomer employed by itself as a layer preferablyis 3.3 to 8.3%, alternatively 4.1 to 7.2%, or 4.6 to 6.2% and the degreeof neutralization preferably is 25 to 100%, alternatively 35 to 80%, or45 to 70%. Higher percent acid and higher neutralization is preferred toobtain improved mar-resistance and clarity or wet look in clear ionomerconstructions for decorative surfaces. For ethylene-methacrylic-acidcopolymers, the weight percent methacrylic acid is preferably greaterthan 8%, more preferably greater than 10%, alternatively greater than12%, preferably in the range of 13-19%. For ethylene-acrylic acidcopolymers, the percent acrylic acid is preferably greater than 7%, morepreferably greater than 9%, alternatively greater than 10%, preferablyin the range of 11-17%. A blend of ionomers can also be employed toenhance mar performance and yet maintain adequate temperatureresistance.

While the neutralizing agent (e.g., zinc oxide, magnesium oxide, andcalcium oxide) can be added in solid form, it preferably is added as aconcentrate in an ethylene-acid copolymer carrier. This concentrate ismade by carefully selecting the ethylene-acid copolymer and the blendingconditions to assure that the neutralizing agent does not significantlyneutralize the carrier. This neutralizing concentrate can also containsmall amounts (up to about 2 wt. %) of one or more salts of the metalcations (e.g. acetates and stearates). The acid copolymer can beneutralized with a mixture of ions by using different neutralizingagents which can provide enhanced mar resistance.

The ionomers of this invention are clear and have low haze levels. Theyalso have outstanding melt strength at thermoforming temperaturesemployed with these skins allowing large parts with deep draws to beformed.

The ionomer layer(s) can degrade and crack during UV exposure. SuitableUV additives such as hindered amines light stabilizers, UV lightabsorbers along with other suitable stabilizers can increase the layersdurability and appearance to withstand extended outdoor exposure.

The surface ionomer layer attracts dust due to electrostatic surfacecharges. Adding anti-stat additives to the top layer and the secondlayer can reduce dust sticking which enhances sheet processing andreduces the potential for surface imperfections in the final article.

Ionomer-polyamide Blend

The ionomer-polyamide blend used in the present invention is one or morepolyamides with one or more ionomers, wherein the ionomer is dispersedin a continuous (or co-continuous) polyamide phase. It preferably ismade by the process taught in U.S. Pat. No. 5,866,658 (incorporatedherein by reference).

The ionomer(s), as more fully set forth above, are preferably directcopolymer(s) comprising ethylene and α,β-ethenically-unsaturated C₃-C₈carboxylic acid wherein the average acid of the direct copolymer(s)prior to neutralization is present in a high percentage and wherein 55to 100 mole percent of the acid is neutralized with one or more metalcations. Preferably the unsaturated C₃-C₈ carboxylic acid is methacrylicacid making up 15 to 25 weight percent of the direct copolymer ofethylene and methacrylic acid or acrylic acid making up 14 to 25 weightpercent of the direct copolymer of ethylene and acrylic acid. Preferablythe metal cation used to neutralize the carboxylic acid also interactswith the amide links of the polyamide. Preferably zinc is used.

The ethylene-acid copolymers used to make the ionomeric copolymersemployed in the ionomer-polyamide blends of this invention have the acidmoiety present in a high amount. The amount that will be considered as“high” will depend on which acid moiety is employed, particularly themolecular weight of the acid moiety. In the case of ethylene-methacrylicacid, the preferred acid level is 13 to 25, (preferably 14 to 25, morepreferably 15 to 22) wt. % of the copolymer. In the case ofethylene-acrylic acid, the preferred acid level is 8 to 25, (preferably9 to 25, more preferably 10 to 22) wt. % of the copolymer. Particularlyin view of the disclosures herein, one skilled in the art will be ableto determine the “high” acid levels for other acid moieties that areneeded to get the desired gloss levels and abrasion resistance.

It will be recognized that it is possible to blend more than onecopolymer, the acid level of any one or more being outside the “high”range of the invention, to obtain an average acid level prior toneutralization that is within the preferred high percentage acid levels.Preferably, in the case of blends, the weight percent acid in each acidcopolymer from which the ionomer components are derived should be closeto the preferred range, and most preferably they should be within thisrange.

The acid moiety is preferably highly neutralized by metal cations,particularly monovalent and/or divalent metal cations. It is preferableto neutralize with metal cations that are compatible with the nylon,that is, with cations that also interact with the amide links of thepolyamide. Preferred metal cations include sodium, lithium, magnesium,calcium, and zinc, or a combination of such cations. Blends of cationsare most preferred. Potassium and sodium are poor choices. Magnesium andcalcium preferably are used in combination with zinc.

The polyamide component, as more fully set forth below, preferably has aviscosity under melt-blend conditions that is high enough to provide themechanical properties but low enough to create the desired phaserelationship. The polyamides comprise semicrystalline polyamides,preferably polycaprolamide (nylon 6). It may also comprise a blend ofsemicrystalline and amorphous polyamides with the amorphous polyamidefraction up to 70% based on total polyamide weight. An amorphouspolyamide that can be used ishexamethylenediamine-isophthalamide-terephthalamide terpolymer.

Preferably, the blend is 60 to 40 (more preferably 50 to 45, also 60 to55) wt. % ionomer and 40 to 60 (more preferably 50 to 55, also 40 to 45)wt. % polyamide (percentages being based on total ionomer andpolyamide). Preferably, the ionomer is dispersed in a reasonably uniformmanner as small, essentially spherical particles for the most part withaverage diameter of preferably about 0.1 to about 0.2 μM in a continuouspolyamide phase. Also, the ionomer preferably is dispersed as oblong andcurvilinear or ellipsoid shaped particles for the most part with anaverage cross-sectional diameter (minor axis length) of about 0.1 toabout 0.2 μM in a co-continuous polyamide phase. The average ratio ofmajor axis length to minor acid length can be about 2 to about 10 orgreater.

The blend may also contain components such as ultraviolet (UV) lightstabilizers, antioxidants and thermal stabilizers, pigments and dyes,fillers, anti-slip agents, plasticizers, nucleating agents, and the likefor both polyamide and ionomer. Preferably, these components are presentin amounts of about 1 to about 3 (preferably about 1.5 to about 3) partsper hundred parts by weight of the ionomer-polyamide blend, but may bepresent in lower or higher levels.

To achieve the desired morphology (ionomer dispersed in continuous orco-continuous nylon phase) using the preferred process, the ionomer musthave a sufficiently high acid level and be neutralized to a sufficientlyhigh level to attain a viscosity greater than that of the nylon. Thepolyamide should have a viscosity higher than that of the ethylene-acidcopolymer or ionomer at low neutralization levels, but should be lessthan the ionomer at high neutralization levels. Preferably, it is madeby first blending a partially neutralized, lower viscosity ethylene-acidcopolymer with a sufficiently high acid level into the nylon and thenfurther neutralizing sufficiently to raise the ionomer viscosity whilemelt blending under intense mixing conditions. Non-neutralized (or lowlyneutralized), high-acid ethylene-acid copolymer can be melt blended withthe polyamide with all of its neutralization being effected during themelt blending. At the high degree of neutralization, the viscosity ofthe ionomer will exceed that of the polyamide at processing conditions.

The preferred level of neutralization will depend on the ethylene-acidcopolymers employed and the properties desired. Neutralization in theblend should be sufficient to raise the melt index (MI) of the ionomerin the blend, measured as grams of ionomer exiting a 0.0823 inch orificein ten minutes (gm/10 min) at 190° C. with 2160 gram weight appliedforce (ASTM D-1238 condition E), to such a level that, if the ionomeralone (not in the nylon blend) were neutralized to that level, therewould be very low to essentially no flow (preferably less than about 0.2grams/10 minutes). For example, for an ethylene-acid dipolymer ofethylene and 19 wt. % methacrylic acid, the following MI values resultwhen the dipolymer is neutralized to the degree indicated:

% Neutralization MI (gm/10 min)  0 60 ~38 2.7 ~52-58 0.71 ~60 0.17 ~670.13 ~90 0 to 0.015

In this case the percent neutralization should be about 60% or greatersince the grams of ionomer exiting the orifice is less than 0.2 gramsper 10 minutes. One skilled in the art can easily determine thepreferred percent neutralization for other ionomers. Preferably in thefinal melt blend with polyamide, the mole percent of acid neutralized is65 to 100%, more preferably 75 to 100%, alternatively 75 to 85%.

The level of acid and the degree of neutralization can be adjusted toachieve the particular properties desired. Gloss is enhanced by raisingthe average acid level. High neutralization yields harder, glossierproducts while more moderate neutralization yields tougher products.

Polyamide

Semicrystalline polyamides can be used in the ionomer-polyamide blendsof the present invention. The term “semicrystalline polyamide” is wellknown to those skilled in the art. Semicrystalline polyamides suitablefor this invention are generally prepared from lactams or amino acids orfrom condensation of diamines such as hexamethylene diamine with dibasicacids such as sebacic acid. Copolymers and terpolymers of thesepolyamides are also included. Preferred semicrystalline polyamides arepolycaprolamide (nylon 6), polyhexamethylene adipamide (nylon 6,6), mostpreferably nylon 6. Other semicrystalline polyamides useful in thepresent invention include nylon 11, nylon 12, nylon 12,12 and copolymersand terpolymers such as nylon 6/6,6, nylon 6/6,10, nylon 6/12, nylon6,6/12, nylon 6/6,6/6,10 and nylon 6/6T.

Amorphous polyamides can be substituted for some of the semicrystallinepolyamide to raise the glass transition temperature (Tg) of the nylonphase and to lower the temperature that this material can bethermoformed at. Up to about 70 wt. %, preferably up to about 25-60 wt.%, of the polyamide phase can be amorphous polyamides. The term“amorphous polyamide” is well known to those skilled in the art.“Amorphous polyamide,” as used herein, refers to those polyamides whichare lacking in crystallinity as shown by the lack of an endothermcrystalline melting peak in a Differential Scanning calorimeter (“DSC”)measurement (ASTM D-3417), 10° C./minute heating rate.

Examples of the amorphous polyamides that can be used includehexamethylenediamine isophthalamide, hexamethylenediamineisophthalamide/terephthalamide terpolymer, having iso/-terephthalicmoiety ratios of 100/0 to 60/40, mixtures of 2,2,4- and2,4,4-trimethylhexamethylenediamine terephthalamide, copolymers ofhexamethylene diamine and 2-methylpentamethylenediame with iso- orterephthalic acids, or mixtures of these acids. Polyamides based onhexamethylenediamine iso/terephthalamide containing high levels ofterephthalic acid moiety may also be useful provided a second diaminesuch as 2-methyldiaminopentane is incorporated to produce a processibleamorphous polymer. Amorphous polyamides may contain, as comonomers,minor amounts of lactam species such as caprolactam or lauryl lactam,even though polymers based on these monomers alone are not amorphous aslong as they do not impart crystallinity to the polyamide. In addition,up to about 10 wt. % of a liquid or solid plasticizer such as glycerol,sorbitol, mannitol, or aromatic sulfonamide compounds (such as“Santicizer 8” from Monsanto) may be included with the amorphouspolyamide.

The amorphous polyamide may be a blend of ethylene vinyl alcohol andamorphous nylon in which the polyamide component comprises about 5 toabout 95 wt. % of the total composition of EVOH plus polyamide,preferably about 15 to about 70 wt. %, and most preferably about 15 toabout 30 wt. %.

Backfill Material

Backfill materials may include a wide variety of polymers. Thesematerials include thermoplastic polyolefins (TPO), polyesters (PET),sheet molding compounds (SMC), acrylonitrile butyl styrene (ABS),polyvinyl chloride (PVC), polystyrene (PS), polyurethane (PU),Polyethylene including low density polyethylene (LDPE), linear lowdensity polyethylene (LLDPE), or high density polyethylene (HDPE), andothers materials. Backfill materials can also incorporate scrap materialrecycled from the sheet making process.

In injection cladding, alternative backfilling processes can be usedwith backfill material such as foam generation or gas injection duringthe backfill injection operation. The high gloss decorative surface canbe maintained with these alternative backfill processes or with fillersin the backfill material.

Through proper skin sheet design, surface defects from glass or otherfillers in the backfill material can be avoided. Glass type filler,typically used for stiffening, often provides a poor surface finish dueto glass showing through at the surface. The use of this skin film canprovide an article which has glass in the backing material forstiffening yet with a surface free of glass surface imperfections.

Tie Layer

Tie layers useful in the present invention include those films wellknown in the art for forming melt-bond layers that adhere to the filmsor substrates to which they come in contact. Co-extrudable adhesivesbased on blends of various polyethylenes are well known. For exampleblends of polyethylene, ethylene/alpha-olefin copolymers, polar ethyleneco- or terpolymers and/or ethylene elastomers or rubbers which areadhesive to the ionomer, or an ethylene copolymer which is adhesive tothe ionomer-nylon alloy, such as ethylene vinyl acetate (EVA), ethylene(meth)acrylate copolymers (EA and EMA), and ethylene butyl acrylatecopolymers (EBA). Others include polypropylene (PP) and maleic anhydridemodified polymers including polypropylenes which are adhesive to TPO orPP and ionomer-polyamide blends, or PET or PETG copolymer resins whichare adhesive to higher copolymer containing ethylene copolymers, orionomer-polyamide blends which are adhesive to nylon copolymers such asElvamide®. Further ethylene based polymer blends, especially copolymerscontaining anhydride grafts demonstrate improved adhesion to theionomer-nylon alloy.

Adhesive layers provide delamination resistance between the surfacelayers and subsequent functional layers during processing and end-use.

Ethylene Polar Copolymers

The ethylene polar copolymers useful in the present invention includegenerally any polymer derived from copolymerizing ethylene and one ormore polar comonomers having and acid or acid related functionality. Assuch there role as a polymeric layer in a multilayer film or sheet maybe similar to the above described tie layer. The ethylene polarcopolymers include polymer made by direct copolymerization or bygrafting and the like. The acid or acid related functionality typicallyinvolves comonomer containing the carboxyl group, esters of the carboxylgroup, acid anhydride and the like including vinyl carboxylates such asvinyl acetate. Thus the ethylene polar copolymer includes by way ofexample (but not limited thereto) polymers such as ethylene copolymerscontaining maleic anhydride, acrylic acid, methacrylic acid, and variousesters of (meth)acrylic acid; i.e., (meth)acrylates. The ethylene polarcopolymers also include the EVA type copolymers.

Other Components

Additives normally compounded into plastics may be included in theblend, for example, ultra-violet (UV) stabilizers, UV absorbers,antioxidants, thermal stabilizers, anti-stat additives, processing aids,pigments and the like. When included, these components are preferablypresent in amounts of about 1 to about 3 (preferably about 1.5 to about3) parts per hundred parts by weight of the ionomer-polyamide blend butmay be present in lower or higher amounts. These components arepreferably present in amounts of about 0.3 to about 3 (preferably about0.6 to about 1.3) parts per hundred parts by weight in the ionomer onlysurface layer.

Of particular importance if the part is to be exposed to ultraviolet(UV) light is the inclusion of one or more UV stabilizers for the nylonand for the ionomer. Typically useful UV stabilizers include:benzophenones such as hydroxy dodecyloxy benzophenone,2,4-dihydroxybenzophenone, hydroxybenzophenones containing sulfonicgroups and the like; triazoles such as2-phenyl-4-(2′,2′-dihydroxylbenzoyl)-triazoles; substitutedbenzothiazoles such as hydroxy-phenylthiazoles and the like; triazinessuch as 3,5-dialkyl-4-hydroxyphenyl derivatives of triazine, sulfurcontaining derivatives of dialkyl-4-hydroxy phenyl triazines, hydroxyphenyl-1,3,5-triazine and the like; benzoates such as dibenzoate ofdiphenylol propane, tertiary butyl benzoate of diphenylol propane andthe like; and others such as lower alkyl thiomethylene containingphenols, substituted benzenes such as1,3-bis-(2′-hydroxybenzoyl)benzene, metal derivatives of3,5-di-t-butyl-4-hydroxy phenyl propionic acid, asymmetrical oxalicacid, diarylamides, alkylhydroxy-phenyl-thioalkanoic acid ester, andhindered amines of bipiperidyl derivatives.

Preferred UV stabilizers and absorbers, all available from Ciba Geigy,are Tinuvin®234(2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol),Tinuvin®327 (2-(3′,5′-di-tert-butyl-2′-hydroxyphenyl)-5chlorobenzotriazole), Tinuvin®328(2-(2′hydroxy-3′,5′-di-tert-amylphenyl)benzotriazole), Tinuvin®329(2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole), Tinuvin®765(bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate), Tinuvin®770(bis(2,2,6,6-tetramethyl-4-piperidinyl) decanedioate), Tinuvin® 928,(Chimassorb 2020 (1,6-Hexanediamine, N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-polymer, Chimassorb 119(1,3,5-Triazine-2,4,6-triamine,N,N′″-[1,2-ethane-diyl-bis[[[4,6-bis-[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)- andChimassorb™944(N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine polymerwith 2,4,6-trichloro-1,3,5-triazine and2,4,4-trimethyl-1,2-pentanamine).

Preferred thermal stabilizers, all available from Ciba Geigy, areIrganox®259 (hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), Irganox®1010(3,5-bis(1,1-dimethylethyl)-4-hyroxybenzenepropanoic acid,2,2-bis[[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]methyl]1,3-propanediylester), Irganox®1076 (octadecyl3,5-di-tert-butyl-4-hydroxyhydrocinnamate), Iragnox®1098(N,N′-hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide),Irganox®B215 (33/67 blend of Irganox®1010 withtris(2,4-di-tert-butylphenyl)phosphite), Irganox®B225 (50/50 blend ofIrganox®1010 with tris(2,4-di-tert-butylphenyl)phosphite), and Irganox®B1171 (50/50 blend of Irganox®1098 withtris(2,4-di-tert-butylphenyl)phosphite).

Preferred processing aids include aluminum distearate and zinc stearate,particularly zinc stearate.

Pigments include both clear pigments such as inorganic siliceouspigments (silica pigments for example) and conventional pigments used incoating compositions. Conventional pigments include metallic oxides suchas titanium dioxide, and iron oxide; metal hydroxides; metal flakes suchas aluminum flake; chromates such as lead chromate; sulfides; sulfates;carbonates; carbon black; silica; talc; china clay; phthalocyanine bluesand greens, organo reds; organo maroons and other organic pigments anddyes. Particularly preferred are pigments that are stable at hightemperatures.

Pigments are generally formulated into a millbase by mixing the pigmentswith a dispersing resin that may be the same as or compatible with thematerial into which the pigment is to be incorporated. Pigmentdispersions are formed by conventional means such as sand grinding, ballmilling, attritor grinding or two-roll milling.

Other additives, while not generally needed or used, such as fiber glassand mineral fillers, anti-slip agents, plasticizers, nucleating agents,and the like, can be incorporated.

Preferably, the mixing and the degree of neutralization for theionomer-polyamide blend should be sufficient to bring about the phaseinversion (higher volume percent ionomer dispersed in the continuous orco-continuous nylon phase) in the mixing equipment. It should berecognized, however, that full inversion may not occur in the mixingequipment but may result from further working of the blend in injectionmolding operations for forming plaques and the like.

Tests Used in the Examples

The differential scanning calorimeter (DSC) cooling exotherm can easilyand quickly be determined and is a useful indicator of morphology andthe sufficiency of mixing conditions for the desired morphology in theionomer-polyamide blend. The DSC cooling exotherm will differ dependingon the nylon used, but can easily be determined by one skilled in theart. Preferably, the DSC cooling exotherm when using nylon 6 should be160° C. to 180° C. when cooling is carried out at a rapid rate (e.g. 30°C. min.). The presence of this exotherm indicates that the desired phaserelationship has been achieved. Higher amorphous polyamide fractions inthe ionomer-polyamide blend will reduce this exotherm in enthalpy andtemperature.

Tensile tests are also useful indicators of the ionomer-polyamide blendproduct morphology. When the morphology is correct, the ratio of Tensionat Break (T_(B)) at room temperature (23° C.) to T_(B) at elevatedtemperature (150° C.) preferably is less than about 12 to 15.

EXAMPLES

The following Examples show various aspects of this invention.

The multilayer sheets in the examples were made on a co-extrusion linethat has 4 extruders and 5 layer capability. The co-extruder line usedwas configured as described above with a co-extrusion feed block for thepurpose of combining the flows into contacting layers. The flows wererouted within the feed block so as to combine the layers prior toexiting the feed block and going into a coat hanger type extrusion die.The combined layers exiting the die flow as a molten curtain verticallyonto a metal roller just prior to a second highly polishedcounter-rotating roll forming a nip with the first roll. The sheetcontacts the highly polished surface for approximately ½ of itscircumference prior to releasing the solidifying plastic to a third rollin the takeoff roller system. The sheet is subsequently taken throughanother nip system between rollers, which pulls the sheet in the system.The sheet is subsequently rolled onto a core creating a roll of sheet orcut to length and stacked.

Example 1

A 2-layer structure of Surlyn®9910/Bexloy® W720, using a clear Surlyn®top layer and a pigmented Bexloy® W720 backing layer was made employinga co-extrusion line. Surlyn®9910 is a 15 wt % acid (EMAA copolymer)which is approximately 50% neutralized. Bexloy®W720 is a polyethyleneionomer blend in which the polyethylene is a HDPE and the ionomer is anEMAA copolymer with 10 wt % acid that is neutralized to approximately70%. The blend is intensively mixed.

Table 1 shows the ingredients feeding the 3 extruders being used in thiscase. These ingredients can be individually fed to each extruder or apre-mixed blend of these components can be fed.

TABLE 1 Extruder A Extruder B Extruder C Sheet Layer Layer 1 (top) Layer3 Layer 2 Extruder Diameter 2.5 2 1.5 (inches) Materials: Surlyn ® 991099% Bexloy ® W720 95% 95% UV Processing  1% Additives PigmentConcentrate  5%  5%

TABLE 2 (equipment processing conditions) Temp Setpoint Profiles:Extruder Extruder Extruder (° F.) A B C Rear Feed Extruder Zone 1 305400 400 Mid Rear Zone 2 325 425 425 Mid Front Zone 3 350 450 450 FrontZone 4 360 475 475 Front Zone 5 375 505 505 Front Zone 6 380 None NoneTransfer Pipes 380 505 505 Feedblock 505 Extruder screw rpm's:  15  65 60 Die (left/center/right) 500/505/500 Feed block plug ID BBCAA Takeoff roll temperatures 70° F.

The 2 material flows originating in the extruders forms a 2 layer sheet.Since 2 extruders are being fed the same materials, the layer thicknessin this case are 6 mil for extruder A and 27 mil for the combined flowsfrom extruders B & C.

This sheet can be thermoformed on a male tool with the Bexloy® W720surface contacting the forming tool. In forming, the Surlyn® surfacemight change due to internal stresses in the sheet resulting in orangepeel or a mottle appearance in the formerly glossy surface. This formedsheet can then be inserted into an injection tool for injectioncladding. Bexloy® W720 would be a suitable backfilling material whichcan be injected onto the Bexloy® W720 side of the formed skin. Ininjection cladding, the Surlyn® surface exposed to a polished tool willsoften and form to the tool surface enhancing the glossy appearance inthe cladded part.

Example 2

A 3 layer structure of Surlyn®9910 (clear)/Surlyn®9910(pigmented)/Bexloy® W720, using a clear Surlyn® top layer, a pigmentedSurlyn® under layer and a Bexloy® W720 backing layer is made as inexample 1.

Table 3 shows the ingredients feeding the 3 extruders being used in thiscase. These ingredients can be individually fed to each extruder or apre-mixed blend of these components can be fed.

TABLE 3 Extruder A Extruder B Extruder C Sheet Layer Layer 1 (top) Layer3 Layer 2 Extruder Diameter 2.5 2 1.5 (inches) Materials: Surlyn ® 991099% 90% Bexloy ® W720 100% UV Processing  1% Additives PigmentConcentrate 10%

TABLE 4 (equipment processing conditions) Temp Setpoint Profiles: (F.)Extruder A Extruder B Extruder C Rear Feed Extruder Zone 1 375 350 375Mid Rear Zone 2 400 375 400 Mid Front Zone 3 400 400 400 Front Zone 4400 500 400 Front Zone 5 400 510 400 Front Zone 6 400 None None TransferPipes 400 510 400 Feedblock 480 Extruder screw rpm's:  15 190 150 Die(left/center/right) 410/510/510 Feed block plug ID BB CAA Take off rolltemperatures 75° F. large, 70° F. small

The 3 material flows originating in the extruders form a 3 layer sheet.The layer thicknesses in this case are 2.5 mil for extruder A (toplayer), 8 mil for extruder C (middle) and 19 mils for extruders B(backing).

This sheet can be thermoformed on a male tool with the Bexloy® W720surface contacting the forming tool similar to example 1 forming. Againin forming, the Surlyn® surface might change due to internal stresses inthe sheet resulting in orange peel or a mottle appearance in theformerly glossy surface. This formed sheet can then be inserted into aninjection tool for injection cladding. Bexloy® W720 would be a suitablebackfilling material which can be injected onto the Bexloy® W720 side ofthe formed skin. In injection cladding, the Surlyn® surface exposed to apolished tool will soften and form to the tool surface enhancing theglossy appearance in the cladded part.

This example exhibits a clear Surlyn®/colored Surlyn® system whichprovides the advantages of color matching in Surlyn® irrespective of thetie layer or backing material layer thickness or material. In addition,less pigment is required to provide a typical color match since Surlyn®has high clarity which is advantageous since less pigment is needed tohide the opacity of less clear materials.

Example 3

A 4 layer structure of Surlyn®9910 (clear)/Surlyn®9910(pigmented)/co-extruded tie layer/Bexloy® W720, using a clear Surlyn®top layer, a pigmented Surlyn® under layer, a tie layer to improveadhesion between layers and a Bexloy® W720 backing layer was made withthe equipment and general approach of the preceding examples.

Table 5 shows the ingredients feeding the 3 extruders being used in thiscase. These ingredients can be individually fed to each extruder or apre-mixed blend of these components can be fed.

TABLE 5 Ext. A Ext. B Ext. C Ext. D Sheet Layer Layer 1 (top) Layer 4Layer 2 Layer 3 Extruder Diameter 2.5 2 1.5 (inches) Materials: Surlyn ®9910 99% 90% Bexloy ® W720 100% 75% LLDPE/25% EPDM 100% elastomer UVProcessing  1% Additives Pigment Concentrate 10%

TABLE 6 (equipment processing conditions) Temp Setpoint Profiles: (° F.)Ext. A Ext. B Ext. C Ext. D Rear Feed Extruder Zone 1 375 350 375 375Mid Rear Zone 2 400 375 400 400 Mid Front Zone 3 400 400 400 400 FrontZone 4 400 500 400 400 Front Zone 5 400 510 400 400 Front Zone 6 400none none None Transfer Pipes 400 510 400 400 Feedblock 480 Extruderscrew rpm's: Die (left/center/right) 410/510/510 Take off rolltemperatures 75° F. large, 70° F. small

The 4 material flows originating in the extruders form a 4 layer sheet.The layer thicknesses in this case are 2.5 mil for extruder A (toplayer), 8 mil for extruder C (middle) and 2 mils for extruder D and 17.5mils for extruder B (backing).

This sheet can be thermoformed on a male tool with the Bexloy® W720surface contacting the forming tool similar to example 1 forming. Againin forming, the Surlyn® surface might change due to internal stresses inthe sheet resulting in orange peel or a mottle appearance in theformerly glossy surface. This formed sheet can then be inserted into aninjection tool for injection cladding. Bexloy® W720 would be a suitablebackfilling material which can be injected onto the Bexloy® W720 side ofthe formed skin. In injection cladding, the Surlyn® surface exposed to apolished tool will soften and form to the tool surface enhancing theglossy appearance in the cladded part.

This example again exhibits a clear ionomer/colored ionomer system withits advantages mentioned previously.

Example 4

In manner similar to that described above, the following multilayeredstructures can be made:

For HDPE backing Ionomer/Ionomer (pigmented)/tie/HDPE

For TPO backing Ionomer/Ionomer (pigmented)/tie/TPO

For PE backing Ionomer/Ionomer (pigmented)/tie/PE

For nylon backing Ionomer/Ionomer (pigmented)/tie/nylon

For PET backing Ionomer/Ionomer (pigmented)/tie/PET

For ABS backing Ionomer/Ionomer (pigmented)/tie/ABS

In a similar fashion, the pigmented Ionomer layer can be eliminated ifthe tie and/or backing layers are pigmented.

Note: backing substrates may be added by filling, foaming, compressionmolding or by other processes.

Example 5

In a manner similar to that described above, ionomer-polyamidestructures can be made. The simplest of these structures will be of theform: ionomer-polyamide (pigmented)/tie layer/backing layer.

Examples with ionomer-polyamide surface layers with the followingstructures are:

For HDPE backing ionomer-polyamide (pigmented)//tie/HDPE

For TPO backing ionomer-polyamide (pigmented)//tie/TPO

For PE backing ionomer-polyamide (pigmented)//tie/PE

For nylon backing ionomer-polyamide (pigmented)//tie/nylon

For PET backing ionomer-polyamide (pigmented)//tie/PET

For ABS backing ionomer-polyamide (pigmented)//tie/ABS

Note: backing substrates may be filled, foamed, compression molded orapplied by other processes.

For making a thermoplastic multilayer ionomer-polyamide/tie/TPO sheet,the following processing conditions can be used. Surlyn® ReflectionsSG201U white M261060 is an ionomer-polyamide blend with white colorcompounded into the resin, EP94592-116 adhesive layer is blend ofpolypropylene copolymer resin, anhydride modified polypropylene andelastomer resin. Solvay TPO E1501 is a rubber modified polypropylenecopolymer.

TABLE 7 Extruder A Extruder B Extruder C Sheet Layer (top) Layer 1 Layer3 Layer 2 Extruder Diameter (inches) 2.5 2 1.5 Materials: Surlyn ®Reflections 100% SG201U white M261060 EP94592-116 adhesive 100% layerSolvay TPO E1501 100% Layer Thickness (mils) 9 3 8

TABLE 8 (equipment processing conditions) Temp Setpoint Profiles: (° F.)Extruder A Extruder B Extruder C Rear Feed Extruder Zone 1 410 400 350Mid Rear Zone 2 450 450 350 Mid Front Zone 3 480 475 400 Front Zone 4480 500 410 Front Zone 5 480 510 420 Front Zone 6 480 none none TransferPipes 480 510 420 Feedblock 510 Extruder screw rpm's: 40 45 55 Die(left/center/right) 510/510/510 Feed block plug ID BBCAA Take off rolltemperatures Primary Gloss roll: 180° F.; Secondary rolls: 120° F.

Example 6

In systems employing ionomer as the top layer and systems employingionomer-polyamide blends, recycle may be incorporated. For the purposeof this example, the Ionomer/Ionomer (pigmented) orIonomer-Polyamide-Blend (pigmented) top layers are referred to as the“Top system.” “Recycle+backing” represents that the recycle is includedin the backing material. Typical structures which might be employed withrecycle are as follows:

-   -   Top system/tie/recycle+backing    -   Top system/tie/recycle/tie    -   Top system/tie/recycle/tie/backing

Having thus described and exemplified the invention with a certaindegree of particularity, it should be appreciated that the followingclaims are not to be so limited but are to be afforded a scopecommensurate with the wording of each element of the claim andequivalents thereof.

The invention claimed is:
 1. A multilayer sheet comprising a firstlayer, a second layer, a third layer; and optionally a tie layer, arecycled polymer layer, or both wherein the sheet is a thermoformablesheet; the combined first layer and the second layer have a thickness of8 to 60 mils; the first layer is a surface layer in contact with thesecond layer and consists essentially of ionomer and a first additive;the second layer comprises an ionomer-polyamide blend and a secondadditive and is in contact with the first layer; the ionomer-polyamideblend consists essentially of at least one polyamide forming acontinuous phase or co-continuous phase with at least one ionomerdispersed therein; the third layer is in contact with the second layer,directly or through the tie layer, and comprises a very low densitypolyethylene and a third additive; the first additive, the secondadditive, and the third additive are individually selected from thegroup consisting of one or more UV stabilizer, UV absorber, antioxidant,thermal stabilizer, anti-stat additive, processing aid, fiber glass,mineral filler, anti-slip agent, plasticizer, nucleating agent, pigment,dye, flake, and mixtures of two or more thereof; and the tie layercomprises a blend of polyethylene, ethylene/α-olefin copolymer, andethylene elastomer; ethylene vinyl acetate; ethylene (meth)acrylatecopolymer; ethylene butyl acrylate copolymer; polyethylene terephthalateand polyethylene terephthalate glycol copolymer resins; maleic anhydridemodified polypropylene; copolymers containing anhydride grafts; or amixture of two or more thereof.
 2. The sheet of claim 1 wherein thesheet is a surface layer of automotive part, appliance panel, oraviation.
 3. The sheet of claim 1 wherein said first layer is clear andsaid second layer contains pigments, dyes, flakes, or mixtures thereof.4. The sheet of claim 1, 2, or 3 wherein the sheet has a thickness of 40to 60 mils.
 5. The sheet of claim 1, 2, or 3 wherein the sheet has athickness of 12 to 40 mils.
 6. The sheet of claim 5 wherein the sheetcomprises the tie layer.
 7. The sheet of claim 6 wherein the tie layeris in contact with both the second layer and the third layer.
 8. Thesheet of claim 1 wherein the sheet has a thickness of 80 to 180 mils. 9.An article consisting essentially of a substrate to which a multilayersheet is adhered, wherein said multilayer sheet is as recited inclaim
 1. 10. The article of claim 9 wherein the first layer is clear andthe second layer is pigmented.
 11. A process comprising positioning athermoformable multilayer sheet into a mold; injection backfilling thesheet with a backfilling material under a condition effective to producean article wherein the multilayer sheet is as recited in claim 1 havinga thickness of 12 to 60 mils; the backfilling material includesthermoplastic polyolefin, polyester, sheet molding compound,acrylonitrile butyl styrene, polyvinyl chloride, polystyrene,polyurethane, low density polyethylene, linear low density polyethylene,high density polyethylene, or mixtures thereof; and the article has aDistinctness of Image (DOI) of at least 80 and a gloss that exceeds 60%at a 20 degree angle.
 12. The process of claim 11 further comprisingconforming said multilayer sheet to a contoured surface of a substratein the mold.
 13. The process of claim 11 further comprisingthermoforming the multilayer sheet to produce a thermoformed sheet andpreheating the thermoformed sheet to produce a softened sheet whereinthe mold has a deep draw, is textured so as to provide a texturedsurface on said article, or is polished so as to provide a gloss surfaceattribute on said article; and the surface of the article substantiallyreplicates the surface finish of the mold.